1. Field of the Invention
The present invention relates to an apparatus and method for controlling an operation of a storm sewage pump utilized in a sewage treatment plant or the like and, more particularly, to a storm sewage pump operation control apparatus and method for controlling the number of storm sewage pumps to be operated in consideration of temporal and spatial variations of a rainfall.
2. Description of the Related Art
A sewage treatment plant is important for sewage works. The sewage treatment plant is also essential to prevent disasters caused by a rainfall, assure sanitation of cities, and maintain good environments. From this point of view, control of the number of storm sewage pumps to be operated as sewage treatment equipment is very important. A difference between an obtained advantage and disadvantage is significantly affected by suitability of control of a storm sewage pump operation.
Rainfall handled in a sewage treatment plant changes in accordance with rainfall characteristics which areally change over time, a configuration of the ground, an arrangement of conduits, a structure of conduits, and the like. For this reason, a change over time of a rainfall in a certain area is not identical to a past one and does not have reproducibility. Such a rainfall property is called temporal and spatial variations of rainfall.
The following conventional techniques are used to forecast such a complicatedly changing rainfall and determine the number of storm sewage pumps to be operated.
1. Ground rain gages are set at a plurality of positions in an urban area. A future rainfall is forecasted by experience of a person on the basis of a rainfall measured by the ground rain gages. The number of pumps to be operated is determined on the basis of the forecasted rainfall.
2. A rainfall in each area is observed by using a radar rain gage. A future rainfall is forecasted by experience of a person on the basis of the observed rainfall. The number of pumps to be operated is determined on the basis of the forecasted rainfall.
3. A water level gauge is set in a well (pump well) from which storm water pumps pump up water. The number of storm water pumps to be operated is determined on the basis of an increase/decrease in water level measured by the water level gauge. This 3rd technique is disclosed in, e.g., Japanese Patent Disclosure (Kokai) No. 57-186080.
The 1st and 2nd techniques largely depend on experience of a person. For this reason, it is difficult to adequately determine the number of storm water pumps to be operated.
An increasing/decreasing rate of the water level of a pump well significantly differs in accordance with a structure of a conduit connected to the pump well, the type of another conduit connected to the distal end of the conduit connected to the pump well, and the like. In addition, in an urban area, along with overcrowding of houses caused by the concentration of population or the spread of paved streets, most of rain water does not penetrate into the ground but flows into sewer pipes. For this reason, since a large amount of storm water must be simultaneously drained to rivers, a storm water pump having a very large capacity has been increasingly Therefore, according to the 3rd technique, even when the number of pumps to be operated is increased on the basis of determination that the water level of a pump well rises, the water level may rapidly fall or vice versa thereafter. Therefore, in the 3rd technique, the number of pumps to be operated must be changed over time in accordance with the water level change in the pump well. This consumes a large amount of power, shortens a service life of a storm water pump, and sometimes adversely affects adequate drainage of storm water from sewer pipes to rivers.